Research Topics

The Dartmouth planetary geomorphology group seeks to understand the rates and histories of processes that shape the Earth, as well as other planetary bodies, like Mars. We focus on understanding processes that have scales ranging from the motion of a single particle to how particles organize to form river bedforms to how rivers build fans and deltas. We use remote sensing data, field studies, and physical experimentation to constrain the rates and histories of these processes, which has implications for quantitatively reconstructing past climate conditions from preserved landforms, extracting the processes that dominate a landscape based on its shape, and determining the extent to which fluids modify a surface.

Our research falls within three main categories: sediment transport on steep slopes, channel morphology, and landscape evolution of planetary surfaces.

Contact me: marisa.c.palucis-at-dartmouth.edu

Sediment Transport on Steep Slopes

Sediment transport in steep mountain channels controls channel morphology and landscape evolution under changing climatic and tectonic regimes, and can pose major hazards to life and infrastructure. However, little is known regarding the mechanisms by which sediment is entrained and transported in steep mountain channels. Even more uncertain is our understanding of the transition from fluvial processes to debris flows. Debris flows have significantly higher sediment concentrations and both solid and fluid forces influence their downslope motion, making them destructive to both humans and infrastructure. Understanding the conditions under which debris flow versus fluvial processes dominate is a key research goal. Recent projects have focused on in-channel debris flow initiation post-fire, debris flow initiation at intermediate slopes (10% > S > 30%), the effect of fines on pore pressure generation and debris flow mobility, and long run-out debris flows on low gradient alluvial fans.

Natural streams rarely have flat beds because mobile bed sediment often forms distinct bed- and channel-forms, such as ripples, dunes, bars, and alternating steps and pools. The presence of these bed morphologies through the channel network is important as they affect hydraulic roughness and flow resistance, which in turn affects flow depth and velocity, sediment transport rates, and bedrock incision rates. Channel state depends on local flow structure, supply of sediment, and forcing/boundary conditions, resulting in feedbacks between hydraulics, sediment transport, and bed topography. Considerable effort has gone into understanding the conditions under which different channel morphologies develop for low gradient sand-bedded streams, but less work has been done for steeper, gravel- and boulder-bedded streams. Current projects have focused on understanding the correlation of bedforms with slope, bedform formation in steep gravel-bed experiments, and how sediment supply affects bedform morphology.

Planetary Geomorphology

Rarely is the full historyof a landscape known such that it is possible to assess how much water was required to produceit. On Mars, the question of how much water has flowed across its surface (and when) has been central to Mars' exploration from the first mapping of channels (“canali”) by Giovanni Schiaparelli in the 1800s to evidence for liquid water at its surface today. Our group uses a mechanistic understanding of surface processes on Earth to apply to Mars, including paleo-reconstruction from sedimentary deposits, investigating possible shorelines, and determining lake-level histories in paleo-crater lakes and basins.